The invention relates to thermoplastic bags which are stacked and blocked or unitized to be configured as a bag block. Furthermore, the invention relates to a method of successively filling the bags and separating the filled bags from the bag block.
The prior art related to the subject matter of the present invention includes U.S. Pat. Nos. 4,451,249; 4,342,564; and 4,699,607; PCT publication WO 99/48677; and European Patent EP 1 036 741, all herein incorporated by reference. Pending U.S. Ser. No. 09/517,968, filed Mar. 3, 2000, is also herein incorporated by reference.
Bag blocks are used in food packaging assembly lines for bagging successively delivered products such as bread loaves. In the manufacture of bag blocks, one approach is described in U.S. Pat. No. 4,699,607 which involves producing two bags from each web segment or sheet wherein each segment is provided with a line of perforations defining a generally circular enclosed area located equidistant from the opposed edges of the sheet. A stack of such sheets is carried by a support, supporting a central medial band of the sheets. The sheets are unitized or blocked by a heated member projecting through the sheets in the perforated circular area of the sheets. To produce individual bag blocks, the sheet stack is cut along a line through the central medial band of the sheets.
For a wicketed bag stack, holes can be prepunched into the sheet within or outside of the circular perforated area, before the sheets are stacked, and posts are provided on the support for receiving the succession of sheets impaled thereon via the prepunched holes. The subsequently blocked stack of wicketed bags is moved to a filling station wherein bags can be dispensed from the bag block by tearing individual bags from the bag block.
Another method of forming a bag block follows the following steps:
unwinding a layer of flat web of film from the unwind stand;
folding the web of film over a folding board;
applying a gusset in the web of film;
entering the web of film into the bag forming machine via the infeed section;
passing the intermittant moving part of the bag forming machine whereby a number of operations are done to the web, including the application of a perforation pattern;
forming the bags by means of a sideweld or mixed weld sealing head;
picking up and stacking bags on an index conveyor or an automated wicket handling system; and
unitizing the stack of bags.
The unwind step can be accomplished by a standard Hudson-Sharp Machine Co. model SDU 1600 unwind stand. It is an electrical surface-driven and braked unwind with a compensator for perfect web tension control. A web guiding system ensures a centered web exiting the unwind stand.
The pre-centered web is pulled over the folding board by the infeed section of the bag machine, thereby forming a J-folded web whereby the lip is typically 35 to 45 mm wide. The folding board is a standard Hudson-Sharp Machine Co. 1500 mm folding board accessory. Optionally a bottom gusset is formed in the J-shaped web. The gusset former is a standard Hudson-Sharp Machine Co. 750 mm gusset former accessory.
The infeed section is the first section of the Hudson-Sharp Machine Co. model 4750W basic wicket machine. It pulls the J-folded web into the bag machine from the gusset former, folding board and unwind by means of a set of nip rolls typically driven by an AC motor. This AC motor is controlled by a frequency controller which obtains a speed reference from the main machine controller and the infeed dancer which is part of the infeed section and located just stream downwards of the nip rolls.
As a standard feature on the Hudson-Sharp Machine Co. model 4750W basic wicket machine, the intermittent moving part of the machine consists of two sets of servo driven nip rolls. In between the two pairs of nip rolls several attachments will modify the web of film such as by punching wicket holes for stacking and/or will detect the photo-eye mark for print registration. The formation of the bag is done in the sealing section of a standard Hudson-Sharp Machine Co. model 4750W. Typically the seals are side seals but mixed weld seals are also possible.
The picking up and stacking of the bags is done in the pick-up and conveyor section of a standard Hudson-Sharp Machine Co. model 4750W. Wicketed bags have wicket holes. Wicket holes have heretofore been circular, triangular, star shaped, or diamond shaped. The bags are stacked on wicket pins going through the wicket holes during stacking. Although this stacking method produces the most ordered stacking quality, it isn""t a necessity. The bags can be made without any kind of stacking holes and be stacked on needles. The unitizing of the stack can be done with a standard Hudson-Sharp Machine Co. pin blocker. Accordingly, heated pins can be driven through the stack of bags. The unitizing is done in the lip area above a region of perforations. The subsequently blocked stack of wicketed bags is moved to a filling station wherein bags can be dispensed from the bag block by tearing individual bags from the bag block. During the filling operation perforations are broken to create an opening of each bag large enough to receive the product being packaged.
A method of filling and separating successive bags is described by the following steps:
putting a stack in a stack recipient box and indexing the box to the bag filling area;
opening the bag with an air nozzle or suction device;
inserting the bag opening device or xe2x80x9cspoons;xe2x80x9d inserting the product into the bag;
pulling the bag off the stack together with the product; and
closing the bag and putting the bag on an offload conveyor.
The Ibonhart model IB 360 filler feeds each stack of bags into the filling area by means of a xe2x80x9crecipient box.xe2x80x9d In a preparation station, an operator puts a stack of bags into a recipient box. When the recipient box in the filling area is empty, it is transferred away from the filling area and a prefilled new recipient box is placed into the filling position. In this process the stacks are presented substantially horizontally in the recipient box. A slight downward angle in the gusset area (i.e., bottom area of the bags when oriented upright) can be applied to lower the gusset area.
Once the filling starts or restarts, bags are removed from the recipient box in the filling station. An air blast, aimed towards the opening of the top bag initially opens the top bag. Once the bag is opened, a set of spoons is inserted into the bag. The spoons engage the mouth of the bag and open it to a somewhat rectangular shape which corresponds to the shape of the product to be packaged. At this moment the bag is held by the spoons but is still connected to the rest of the stack by means of the wicket wire via the wicket holes. By means of a pusher the product is pushed into the bag. When the product hits the bottom of the bag, the still moving pusher will rip off the bag from the stack over the wicket wire. According to another known method, the spoons open the bag and then draw the bag in a reverse direction to the direction the spoons entered the bag, i.e., in a forward direction, to separate the bag from the block and at the same time to capture a stationary product within the moving bag. According to either method, the product together with the bag is then brought into another area of the filler where the bag is closed and transported for further handling.
As the stack is depleted, the recipient box is moved vertically upward to maintain an equal filling plane. The filled bag is pulled off the stack, over the wicket wires. Since the bag is completely removed after each fill, the top of the remaining stack has full clearance without leaving any scrap which could interfere with the filling process. However, the entire lip is removed with the bag which can constitute an undesirable extra flap connected to each bag.
Another method of filling a succession of bags is described in Australian published application AU 20002280 A1. According to this reference, a stack of bags is positioned on a support. The stack is held on holding rods and a flap region of the stack is clamped to the support. In this disclosure, the act of opening the bag breaks angularly oriented lines of perforations and substantially severs the top bag from corner portions of the bag flap entirely or except for short unperforated parts adjacent to the top edge of the bag. A product, such as a loaf of bread, is inserted into the open mouth of the bag and the bag with product inside is separated from the corner portions of the bag flap by breaking the short unperforated parts if they are present. A considerable amount of flap material is included with the separated bag. As the height of the bag decreases, the stacking table is moved up against the clamping plate.
The present inventor has recognized the desirability of providing bags to be dispensed from a block of bags, wherein the bags are unitized in a bag block, each bag having a lip, wherein individual bags can be removed from the block with a minimized portion of the lip connected to the separated bag. The present inventor has also recognized the desirability of providing a method of filling such bags, wherein the bags are filled and successively torn from the block, wherein the lip portions remaining on the block do not interfere with the filling of subsequent bags.
The present invention contemplates an improved design for wicketed and wicket-less blocked bag stacks or bag blocks wherein the bags are unitized within a lip or flap area thereof, and wherein a top bag body of the block is removed from the stack with a minimally-sized lip portion of web material adjoined thereto.
In a first aspect of the invention, two edge lines of perforations extend inwardly from edge points on respective side edges of the bag, for a short distance. A central line of perforations extends between the two edge lines of perforations, offset from the edge points toward a top edge of the bag. Preferably, the central line of perforations is less easily torn than the two edge lines of perforations. The edge lines of perforations can be perpendicular to the side edges and parallel to the central line of perforations, or can be oblique to the side edges and to the central line of perforations. The central and two edge lines of perforations can be joined together by oblique or perpendicular line segments or curve segments of perforations, preferably being perforations which are easily torn, similar in degree to the tear strength of the first and second edge lines of perforations.
A plurality of such bags are collected in a stack. A hot plate or pin is driven through corner lip areas defined by the adjacent side and top edges of each bag, and the two lines of perforations, and a hot plate or pin is driven through a central lip area defined between the top edge and the central line of perforations, to unitize or block the stack of bags.
This embodiment can be incorporated into a wicket-less or wicketed bag. In the case of a wicketed bag, two wicket holes can be provided between the top edge and the central line of perforations.
During a filling operation, the top bag is opened from a flat to a rectangular or pillow configuration with a substantially rectangular open mouth, adjacent to the lip. During the opening, the two edge lines of perforations, which are easily torn, separate or tear to accommodate the rectangular shape of the mouth. After the bag is filled, it is forcibly torn along the central line of perforations to separate the bag body from the bag block. The bag once separated, includes only a short lip portion, taken in a longitudinal direction of the bag. The bag block retains the remaining lip portion from the separated bag. As more bags are removed, the remaining lip portions of the previously separated bags can become an obstacle to filling subsequent bags, unless inventive apparatus are utilized.
In this regard, according to a second aspect of the invention, the bag block is held on a support platform during filling, wherein the support platform includes an obliquely oriented lip support with an associated clamp which holds the remaining lip portions to the lip support. The remaining lip portions are held below the elevation of the bottom bag, such that remaining lip portions will not interfere with filling the entire stack of bags, beneath the original top bag.
In another aspect of the invention, two substantially rectangular corner tear-off regions are provided at the upper corners of a bag. The corner tear-off regions are each substantially defined by one lateral edge of the bag, the top edge of the bag, one edge line of perforations as described in the first embodiment, and one of two short lines of perforations extending substantially from the one edge line of perforations to the top edge of the bag.
Wicket holes can be provided within a central region of the lip. A hot plate or pin is passed through the stack of bags, within each of the corner tear-off regions, and through the central region of the lip, to unitize the stack of bags as a bag block.
The corner tear-off regions are removed before the block reaches a filling station. Preferably, plural stacked corner regions are removed together from a formed bag stack or bag block by clamping the corner regions and clamping the remaining bag stack or block separately and differentially moving the two clamping mechanisms to separate the corner regions from the stack or block. Alternately, the corner regions are removed from each bag during bag formation on the bag forming machine. The corner tear-off regions are clamped, and the remaining bag is separately clamped. Using differential movement between the clamps, the corner regions are removed from the bag by tearing along the perforations. It is also possible that the bag block with corner regions attached thereto is shipped to the filling station, such as a bakery, where the corner regions are removed prior to or during filling. The corner tear-off regions are removed before the filling operation to facilitate the initial opening of the bag mouth from a flat condition to a rectangular shape.
Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.